This invention relates to a sealing device for sealing against a cylindrical surface. In a particularly preferred form, the device seals against two cylindrical surfaces which define between them an annular space. The space may be a space between two pipes of different diameter, one arranged inside the other. A typical situation where such a seal is required is in a subterranean well bore, for example an oil or gas well.
The term xe2x80x98cylindricalxe2x80x99 used in this specification is not to be construed as requiring perfect circularity. The invention is applicable to out of round surfaces, even elliptical, oval or irregular surfaces.
The invention is not however limited to use in well bores.
Difficulties are often encountered in setting a high-integrity, fluid and gas-tight seal in an annular space where direct access to the space cannot be had. The invention seeks to provide a seal which can travel along an annular gap and can then be set or tightened at a particular position in such a gap and which is capable of sealing between two pipes which may be uneven and/or eccentric.
According to the invention, there is provided a sealing device for making a seal against a surface, the device comprising at least one flexible seal ring having a relaxed position in which it is out of contact with the surface and an active position in which it is in sealing contact with the surface, an operating member movable relative to the seal ring in a direction substantially parallel to the cylindrical surface to produce a substantially radial movement of the ring into its active position, and a plurality of elongate shape-memory material actuators arranged around the operating member so that a change of shape of the actuators produces the movement of the operating member which moves the seal ring into its active position.
The invention also provides a method of setting a seal against a surface, using a seal ring which is to be radially deformed to make sealing contact with the surface, wherein an operating member is movable relative to the seal ring in a direction substantially parallel to the cylindrical surface to produce a substantially radial movement of the ring into its active position, and a plurality of elongate shape-memory material actuators are arranged around the operating member so that a change of shape of the actuators produces the movement of the operating member which moves the seal ring into its active position.
The actual form of the seal ring is not significant to this invention. The invention however provides a mechanism for setting a seal ring into the sealed position.
The use of a shape-memory material allows the actuation of the seal to be triggered merely by providing some method for changing the temperature of the sealing device once it has reached its intended position. Heat can for example be generated electrically or chemically to actuate the seal, thus avoiding the need to apply mechanical force at a remote location. The heat can be generated internally, within the device or externally by a separate piece of equipment temporarily or permanently placed in proximity to the device.
The preferred method of actuation is for the actuators to contract rather than to expand because the contraction movement of a shape-memory material is substantially larger than an expansion movement.
The device preferably includes a main body component, part of which forms the seal ring. The actuator and the operating member are then connected to the main body. The main body is preferably a continuous component with no leak paths therethrough.
The operating member and the actuator can be formed from a single piece of shape-memory material, or they can be formed from separate pieces of material, with the actuator connecting the operating member to the main body.
In a preferred form of the invention, the main body has a skirt portion, the seal ring is formed at the free end of the skirt and the main body includes a secondary portion for sealing the cross-section surrounded by the cylindrical surface.
The skirt allows the seal ring to be connected to the main body, and yet to have sufficient freedom of movement (through flexing of the skirt) to allow the seal ring to move between its relaxed and active positions.
The cylindrical surface can be an internal cylindrical surface (the inside of a pipe) with the secondary portion of the main body being a continuous plug adapted to extend across the pipe bore to block the bore. Alternatively the cylindrical surface can be an external cylindrical surface (the outside of a pipe) with the secondary portion being a continuous cap adapted to close the pipe bore, a seal for seating a valve, tool or other device in the bore or a connector for another pipe or tool.
However the device can be used to seal an annular gap between two concentric or near concentric pipes. In this case the secondary portion of the main body will be a second skirt having a second seal ring adapted to seal against the inner of the two pipes.
The shape-memory material actuator rods preferably all have parallel axes extending parallel to the cylindrical surface and are preferably regularly spaced around the cylindrical surface. Alternatively however the actuator could be in the form of a cylindrical collar of shape-memory material or of a number of segmented portions. The rods will be housed in a cylindrical annular space between the skirt and the main body, and can have threaded ends which screw into threaded bores in the main body.
The operating member is preferably an annular ring with a tapered surface for contact with the seal ring to produce the radial movement of the ring when the tapered surface is moved axially relative to the ring. The annular ring can have one or two tapered surfaces, depending on whether there are one or two seal rings.
The annular ring can be continuous around the cylindrical surface, and can have a cross section which varies around the circumference, with the variation repeating itself between each shape-memory material rod attachment point. Alternatively the annular ring can be divided into separate segments around the cylindrical surface.
The cylindrical annular space in which the shape-memory material actuator is housed preferably has a vent opening to allow the escape of trapped fluid or gas as the volume within the space is reduced by movement of the seal ring into the space. This vent is preferably provided in the operating member and may have a one-way valve to prevent external atmosphere of foreign matter from entering the space.
The cylindrical surface is preferably of metal, and the seal ring can have a metal sealing surface so that a metal-to-metal seal is established by the device.
The tapered surfaces can have regions of different slope, so that the radial cam action of the tapered surfaces on the seal ring varies during the course of the relative movement between the operating member and the seal ring. At least part of the tapered surfaces preferably have a slope such that a self-locking action is produced by the friction between the tapered surfaces and the seal rings. This ensures that if the actuator should, during service, break or otherwise relax the force which produces the engagement between the operating member and the seal ring, then the operating member will stay in place.
The device may include within itself means for activating the shape change of the shape-memory material actuator. For example induction heating means may be included in the device.